AHU (Air Handling Unit)

An AHU (Air Handling Unit) is a larger relative of the FCU: instead of cooling one room, it conditions air for a whole floor, zone or common area and pushes it through ducts to many outlets. It houses filters, a chilled-water coil and a large fan, and you'll find AHUs serving office floors, hotel and mall areas, building lobbies and some larger villas and duplexes. The practical difference for a resident: an FCU is small and room-level, and it's yours to maintain; an AHU is plant-room or zone-level, and it's usually building-maintained — so in an apartment you rarely touch one, but in a villa or duplex a small AHU may serve an entire floor and does need its filters, coil and drain serviced. If a whole floor cools unevenly or smells musty, the AHU (not a single FCU) is often the culprit and is a chilled-water system specialist's job.